The present invention relates generally to auto-focus cameras, and more particularly to an automatic range finder device which may be included in an auto-focus camera such as may be found, in accordance with U.S. Patent Office classification, in Class 33, Sub-class 284, or Class 95, Sub-class 44, or Class 250, Sub-class 204.
In the past, most automatic focusing systems have required two basic motions. One is a motion of a focusing lens with respect to a plane upon which a focused image of a scene is to be formed. The second motion is a scanning motion of a light detector with respect to the image at that or a related image plane. Some focus detecting systems have been developed which obviate the requirement of scanning the image plane in order to determine the best focus position of the objective lens. However, those systems have introduced other disadvantages such as being optically complex, costly, and relatively inaccurate.